Hepatitis B virus (HBV) is a member of the Hepadnaviridae family and is a major pathogen causing acute and chronic viral hepatitis in human. Two billion people have been infected worldwide, of which more than 350 million have chronic HBV infections (WHO statistics data). HBV infection is endemic in certain areas in Asia. The prognosis of viral hepatitis B is especially poor in patients who were infected perinatally and suffered from chronic viral hepatitis B with replicative HBV infection, wherein usually serum Hepatitis B e Antigen (HBeAg) is persistently present. Over the years the patients have high probability to develop complications such as liver cirrhosis and hepatocellular carcinoma.
Hepatitis B is transmitted via body fluids containing the virus. The most common routes of HBV transmission are blood or other blood products transfusions, re-use of contaminated needles, unprotected sexual contact, and vertical transmission from mother to infant during childbirth. Ninety percent of infants infected may develop chronic HBV infection later in life.
Prevention is the primary way to stop HBV transmission among population at present. Safe and effective recombinant vaccines are available for prevention of HBV infection, and vaccination programs for general public are common practice in many countries now.
No effective way to cure chronic HBV infection has been established. The US Food and Drug Administration (FDA) has approved five drugs (lamivudine, entecavir, adefovir dipivoxil, interferon alfa-2b and pegylated interferon alfa-2a,) for the treatment of patients with chronic hepatitis B. The drugs are known to inhibit the replication of HBV and thus can slow down the course of the disease and the development of complications. However, less than 30% overall response rates and dose-dependent side effects restricted the use of interferon alpha. On the other hand, prolonged use of lamivudine, entecavir and adefovir dipivoxil to emergence of drug resistant HBV mutants also limited its use for long term therapy of chronic hepatitis B patients. Post-exposure prophylaxis with hepatitis B immune globulin is also known effective to prevent non-immune individuals from the infection after an exposure such as a needle stick. Yet chronic hepatitis patients face uphill battle to achieve their HBV virus free state, and new anti-HBV target which may substitute or complement the above mentioned drugs leading to cure HBV infection still awaits for the development of medical research.